Contact assembly and control structure



Sept. 29, 1959 G. J. MUCHER ETAL 2,906,984

CONTACT ASSEMBLY AND CONTROL STRUCTURE Filed May 9, 1956 INVENTORS fieog'q [lurker lilden [Packard J0 ATTORNEYS United States Patent ice CONTACT ASSEMBLY AND CONTROL STRUCTURE George J. Mucher, Rochester, and Alden Richard Jo'y, Dover, N.H., assignors to Clarostat Mfg. (10., Inc., Dover, N .H., a corporation of New York Application May 9, 1956, Serial No. 583,849

3 Claims. 01. sss 171 This invention relates to a structurally and functionally improved contact assembly and control for use in electrical apparatus.

By means of the present teachings, a control apparatus is furnished in which the several parts may be shifted with respect to each other to vary the electrical values within a circuit and in which, with that control employed in certain preferred installations, there will be'a minimum of disturbance or distortion in a signal transmitted by the circuit.

A further object is that of furnishing an assembly of this nature in which wear will be reduced to a minimum and in which resistance to moving the parts will be likewise reduced.

Still another object is that of designing a contact assembly for use in an electrical control and which assembly will embody a structure cooperating with maximum efficiency with, for example, a resistance path or track and a collector ring.

Among other objects are those of furnishing structures which will include relatively few and individually simple and rugged parts capable of ready manufacture and assembly to furnish unitary structures operating over long periods of time With freedom from all difiiculties.

With these and other objects in mind, reference is had to the attached sheet of drawings illustrating one practical embodiment of the invention, and in which:

Fig. 1 is a face view of the base portion of an electrical control or casing removed therefrom and a contact assembly in association therewith;

Fig. 2 is a transverse sectional view taken along the line 22 in the direction of the arrows as indicated in Fig. 1;

Fig. 3 is an exploded perspective view of a preferred form of the control and contact assembly; and

Fig. 4 is a perspective face view of the contact memher of that assembly.

Referring primarily to Fig. 2, the numeral 5 indicates the body of a control formed of non-conducting material. Suitably attached to this body and adjacent the rear face thereof may be a mounting plate 6 supporting a rearwardly extending bushing 7 through the bore of which an operating shaft 8 projects. That shaft has rotatable bearing with the surface of the bushing and is prevented from moving inwardly beyond a predetermined point by, for example, mounting a split washer or C-ring 9 within an annular groove formed in its surface and which ring bears against the outer edge of bushing 7. Base 5 conveniently mounts a cap or cover 10 which may be formed of sheet metal and retained thereon in any desired manner. That cover may have an inwardly indented portion 11.

A resistance path or track is provided as part of the control by, for example, recessing the face of body 5 and disposing within that space a ring 12 of resistance material. The body of this ring may be formed by a moulding operation and that body may be bonded likewise by a moulding operation to base portion 5 so that, in effect,

Patented Sept. 29, 1959 a single integral unit is furnished, with the resistance track exposed upon the face of the unit. A ring 13 of suitable metal is likewise disposed within a recess formed in base 5 and preferably adjacent the bore 14 thereof. Element 13 provides the contact ring for the assembly and as shown is spaced from ring 12 by a mass of insulating material integral with base 5; both rings 12 and 13 having their operative faces preferably disposed'in the plane of the adjacent face of the base. A terminal 15 may be formed integral with ring 13 and extend beyond the side edge of base 5. Likewise, terminals 16 may be connected one each to the opposite ends of the resistance path or track provided by ring 12. The base 5 in line with the zone of the terminals 15 and 16 may include an integral extension 17 providing an abutment furnishing maximum support for the terminals.

Secured to the inner end of shaft 8 at a point beyond that face of base 5 which includes the collector ring and resistance path surfaces, is a contact driver. To this end, shaft 8 provides a reduced, non-circular portion 18 terminating in a headed surface 19. A plate 20 includes a central portion apertured to receive the shaft end. It also includes a pair of arms 21 formed adjacent their ends with openings 22. The material of this unit involves at least limited resiliency such that the arms 21 may flex and will return to a normal position in which, in the embodiment illustrated, they will extend inwardly of the headed end 19 of shaft 8. A second plate 23 is interposed between the body of plate 20 and the shoulder defining the end of the reduced end portion 18 of the shaft. This plate is formed with an extension 24 which projects through a notch 25 formed in the edge of plate 20. An outwardly extending portion 26 provides an integral part of plate 23 and, in cooperation with the indented portion 11 of casing or cover 10, furnishes a stop structure limiting rotation of the shaft. As is obvious, when the latter is turned, both plates 20 and 23 will rotate as a unit therewith.

According to the teachings of the present invention, a contact member is provided which is rigid and bridges the space between the resistance path or track 12 and contact ring 13. This contact has been shown especially in Figs. 2, 3 and 4 and includes two layers 27 and 28 of suitable materials which, for example, under heat and pressure are moulded together to, in effect, provide a single integral unit. Layer 27 is formed of a highly dielectric material whereas layer 28 involves a highly conductive composition. At the time of moulding or otherwise, layer 27 is formed with projections 29 preferably in the form of cones extending from its outer face and spaced a distance equal to the spacing of the openings 22 in the different arms 21 of the driver. Layer 28 has formed on its outer face wiping portions or lugs 30 and 31. The former is disposed adjacent the outer edge of layer 28 Whereas the latter are arranged to extend adjacent the inner edge of the same. In this connection, it will be noted that the contact provided by these two layers may, as illustrated, be ring-shaped. As will be apparent, however, it may include any alternative outline embracing, for example, a triangle.

With contact 30 adjacent the outer edge of the assembly, it will traverse contact path 12 if it is suitably rotated around an axis. Similarly contact portions or lugs 31 will traverse the surface of ring 13. Such rotation of the contact member is assured by having the cones 29 extend through openings 22 as illustrated in Fig. 1. This will dispose these portions to either side of the axis defined by shaft 8 and to one side of a line intersecting that axis. In this manner, the central opening embraced in the contact will have its edges concentrically disposed with respect to the surface of shaft 8.

As will be noted, the two cones are in a line substantially midway between the collector or contact ring 7 13 and the contact provided by the projection 30. Accordingly, the force applied by the spring arms 21, upon the shaft 8 being moved outwardly to the final position shown in Fig. 2, is thus distributed between the three contacts 30 and 31. This will assure a firm contact of all the brush portions in spite of any irregularities embodied either in the resistance path or the collector ring surface. Obviously, the line of the cones may be shifted outwardly or inwardly by suitably modifying the parts of the contact driver provided by plate 20 and having the cones 29 at different distances from the edges of the contact element. In this manner, the distribution of the load may be varied as desired. Placing the collector contacts or brush portions 31 at a maximum distance from element 30 has the result that any irregularities in the resistance path or track will effect the smallest possible angular displacement of the contact brush thus insuring maximum radial contact of that unit. In this manner, disturbance in the signal transmitted by the apparatus with which the control is associated is minimized and premature wearing of the parts is also reduced to a maximum extent. V t

In certain ways, one might liken the construction to one involving a three-point support embracing projections 30 and 31 and a two-point support embracing cones 29 and the edges defining openings 22; the latter being dis posed within an arc extending to one side of the shaft axis. Of course, a lesser or greater number of contact projections might be embodied in the contact. Likewise, and as afore brought out, the relationship of the supporting units provided by cones 29 might be varied with respect to the shaft. Rather than having the contact of triangular or other arbitrary outline, it is preferred that a ring-shaped structure be resorted to as shown, in that round forming dies may more readily be made. The openings 22 are slightly smaller in diameter than the base portions of the cones or similar protuberances 29. In this manner, one is assured at all times of a positive driving connection between the driver and the contact.

The wafer provided by layers 27 and 28 should, in effect, be completely rigid under all strains to which it is subjected. The distance between the collector ring on one side of the shaft and the resistance element or pathv on the other side of the same is efiiciently bridged. The low resistivity of layer 28 assures an efficient current path which will be completely insulated from the shaft and its associated elements. The area of the surfaces presented by projections 31 and the elongation of the surface included in the apex portion of projection 30 will assure a low resistance and efiicient contact.

While it is preferred to have the cones 29 on the contact and the openings or recesses 22 on the driver, it will be understood that the arrangement might be reversed.

Thus among others, the several objects of the invention as specifically aforenoted are achieved. Obviously, numerous changes in construction and rearrangements of the parts might be resorted to without departing from the spirit of the invention as defined by the claims.

We claim: a 1. In an electrical control device a body, a collector ring having a surface formed of an electrically conductive material mounted on said body, a resistance ring mounted on said body having a surface concentric with said collector ring, a shaft extending through and rotatable with respect to said body in either a clockwise or a counterclockwise direction, a driver member fixed against rotation with respect to said shaft, a resilient arm integral with said driver member and spaced from said shaft, a second resilient arm integral with said driver member and spaced from said shaft in spaced relation with said first resilient arm, a circular opening formed in said first resilient arm, a second circular opening formed in said second resilient arm, a contact member, a conical projection of said contact member formed with its base of larger diameter than that of said first circular opening and its apex of smaller diameter than that of said first circular opening, a second conical projection of said contact member formed with its base of larger diameter than that of said second circular opening and its apex of smaller diameter than that of said second circular opening, said first conical projection disposed within said first circular opening and said second conical projection disposed within said second circular opening and said resilient arms yieldingly pressing said projections within said openings and urging the contact member toward said body, a raised portion of said contact member engaging said surface of said collector ring and forming a point contact, a second raised portion of the contact member engaging said surface of said collector ring and forming a second point contact spaced from the first point contact, and a third raised portion of said contact member engaging said surface of said resistance ring at a point spaced from said first and second raised portions to form therewith a three-point support for said contact member.

2. An electrical control device as claimed in claim 1 wherein said resilient arm and said second resilient arm integral with said driver member are spaced on opposite sides of said shaft.

3. An electrical control device as claimed in claim 1 wherein said third raised portion of said contact member defines a wedge shaped projection and wherein said third raised portion is located at a maximum distance from said first and second raised portions whereby irregularities on the surface of said resistance ring effect minimum angular displacement of said contact member and permits maximum radial contact of said contact member.

References Cited in the file of this patent i UNITED STATES PATENTS 1,612,955 Valverg Jan. 4, 1927 1,749,662 Browne Mar. 4, 1930 2,000,177 Kenney May 7, 1935 2,514,682 Tellkamp July 11, 1950 2,705,273 De Bell Mar. 29, 1955 2,705,749 Daily et a1. Apr. 5, 1955 2,764,657 Rosenthal Sept. 25, 1956 2,766,359 Craddock Oct. 9, 1956 

